1. Field of the Invention
The present invention relates to a ceramic-coated metal sheet having an excellent decorative property and a high weatherability, which can be used as decorative materials, such as interior materials, construction materials, automobile materials and the like, even under environments where they are actually used.
2. Description of the Related Art
With development and maturation of techniques of electronics, a dry coating process such as physical vapor deposition or chemical vapor deposition has been practically utilized for the surface modification of metal materials. By dint of the progress of this technique, it has become possible to obtain ceramics-coated metal materials provided with such functions as weatherability, abrasion resistance, decorative property and far infrared characteristics, which could not be obtained by the conventional wet process represented by plating. However, this technique involves serious economical problems in that it is not suitable for mass production, the running cost is large and the apparatus is expensive. Therefore, the dry process cannot successfully replace the wet process on an industrial scale unless especially excellent performances or functions are attained.
In the field of decorative materials, gold-color decorative coating of TiN is the almost only instance of successful industrialization while reflecting the recent trend toward high-quality products. As a decorative coating substance, the color of which is utilizable, substances other than the above-mentioned TiN showing a gold color are hardly known. Accordingly, it is very difficult to provide a variety of colors, and only several colors such as gold, black and grey colors are attainable at the present.
A variety of colors can be produced by so-called interference colors, namely by utilizing the interference of light (see, for example, Japanese Patent Application No. 54-66385 and Japanese Patent Application No. 54-85214). In case of an interference color produced by an oxide or nitride of aluminum or silicon, which are customarily used, the color greatly changes according to the viewing angle, and furthermore, since the range where the hue can be controlled by changing the thickness is narrow, the usefulness of the product as a decorative article is very low.
It is an object of the present invention to provide a coated metal sheet having an excellent decorative property and a high weatherability, in which by laminating a transparent ceramic layer having a high refractive index on a metal substrate or a colored ceramics layer formed on a metal sheet, and greatly changing the hue of the metal sheet or colored ceramics, the variety of colors can be increased and the above-mentioned problem of the extreme change of color according to the viewing angle can be solved to some extent.